Heat stencilizable stencil



United States Patent 3,250,637 HEAT STENCILIZABLE STENCIL Paul E. Frasher, Chicago, Abraham D. Davis, Dolton, and Hersh A. Platkevich, Chicago, Ill., assignors to A. B. Dick Company, Niles, Ill., a corporation of Illinois No Drawing. Filed July 7, 1961, Ser. No. 122,423 2 Claims. (Cl. 11735.5)

The present invention relates to a stencil of the type having a coating thereon which will react when subjected to heat to provide an imaged area.

relatively non-infra red ray absorbing material and is ink.

impervious. Therefore, when the stencil is placed on a duplicating machine ink will penetrate only in the stencilized image area and multiple copies may be produced.

The conventional materials employed for the displaceable coatings have been employed in relatively large amounts to provide a sufficiently strong stencil sheet. Furthermore, the thickness of standard stencil sheets of the thermographic type has been excessive due to the fact that the coating materials employed are not sufficiently abrasion resistant to permit the use of thinner coatings.

These attributes of prior stencils of the type described add to the cost of the items and it is therefore an object of this invention to provide a more economical and otherwise improved stencil of the thermographic type.

It is an additional object of this invent-ion to provide a heat stencilizable stencil with a heat displaceable, ink impervious coating which need not-be employed in relatively large amounts to provide a satisfactory stencil.

It is a further object of this invention to provide an improved thermographic stencil with a coating having the above noted properties and also having suflicient abrasion resistance whereby the use of thinner coatings is made possible.

These and other objects of this invention will appear hereinafter and it will be understood that the various examples hereinafter set forth are provided for purposes of illustration and not for purpose of limitation.

The heat stencilizable stencil of this invention is characterized by a light weight and thin base sheet having a coating composed of various amounts of a hard, high melting point wax, with or without parafiin wax, and wax soluble polymer additives.

The base sheet employed in the therm-ographic stencil of this invention comprises a sheet of thin, porous tissue having a weight from 4 to 7 pounds and preferably 4 to pounds per 3,000 square feet of tissue. The tissue employed is a standard stencil base sheet insofar as composition is concerned, such as is formed of yoshinofiber, synthetic organic fiber or mixtures thereof, and it is preferably provided in thicknesses of from 0.8 to 1.2 mils, although thicknesses up to 2 mils are contemplated. The porosity, as measured on a Gurley Permeameter-4 ply, is preferably above 200 cu. ft./ sq. ft./min.

The coating which is applied to the described tissue is composed of from 50 to 100% of a hard, high melting point Wax. The melting point of the wax should fall within the range of 160 to 210 F., and preferably is 190 to 195 F. or 200 to 210 F. The hardness of the wax (100 gr./77/5 sec.) (ASTM D132l-6lT) preferably falls within the range of 5 to 10, but may fall within the broader range of 0 to 20.

The coating may include from 0 to of any commercial parafiin wax and is preferably formulated to contain from 10-35 percent by Weight of the paraffin wax. Likewise a Wax soluble polymer can be added to increase the toughness and oil resistance of the coating in an amount within the range of 0-5 percent by weight and preferably 1-4 percent by weight. Suitable polymers maybe selected from the group consisting of the copolymers of vinyl acetate and vinyl stearate, the copolymers of ethylene and vinyl acetate, and the copolymers of ethylene and ethyl acrylate.

As suggested above, the coating can be formulated of the high melting point wax having the above describedc-haracterist-ics alone, and the waxshould be coated on the tissue to obtain a weight of from 4 to 10 pounds per 3,000 square feet.

Further examples of a suitable coating are as follows:

Example A Percent 190195 Be Square wax (Bareco WaxCo.) 70 l30-l32 parafiin 27 Dow resin X3488.3 3

10 Example B 190-210 F. High M.P. Wax (Be Square wax) 65 Parafiin wax 31 Vinyl acetate-vinyl stearate copolymer 4 This Wax mixture should be coated on the tissue to obtain a weight between 4 to 10 pounds per 3,000 square feet.

As a specific example of the application of this invention to the formation of a stencil, a mixture of the foregoing Example A was dissolved in hot toluene (140150 F.) at a solids content of 25%. The solution was coated onto a 4.5 lb. (24 x 36--500) stencil base tissue at a coating Weight of 5 to 6 pounds per 3,000 square feet and thendried.

In use, the stencil is placed adjacent an original having infra red ray absorbing, heat generating outlines thereon, and the assembly is subjected to a source of infra red radiation. Upon directing of a sufiicient quantity of radiations rich'in infra red onto the original, a temperature rise from ambient temperature to a temperature in the range of from F. to 210 F. is realized in the imaged portion of the original to provide a heat pattern, The coating composition in the corresponding areas on the stencil sheet is reduced to a flowable condition and displaced upon transfer of the heat pattern whereby openings in the stencil sheet are provided through which ink can flow. The original may be employed in the form of a separate sheet or it can be present as an image applied directly to the stencilizable sheet.

The heat stencilizable stencils of this invention are particularly suitable for use in conjunction with an assembly described and claimed in applicants copending application entitled Assembly for Imaging Heat Stencilizable Stencils, Serial No. 122,587, filed July 7, 1961. The assembly described in the copending application generally comprises a top sheet of a relatively infra red transparent, poorly heat conductive shield; a protective, infra red transparent film located beneath the top sheet; and an infra red transparent, heat conductive film located adjacent the protective film. The stencil sheet of this invention is adapted to be fitted between the protective film and the heat con- 'ductive film, and the original will be located beneath the heat conductive film. Stencils produced with an assembly Patented May 10, 1966 of this type are particularly free of objectionable background and dust or dirt on the original or on the belt or plate of the device used for imaging the stencil is effectively avoided. V

The above described stencil is characterized by the use of a thinner base sheet which permits the application of a lighter coating on the base sheet. It is appreciated by the art that thinner stencil sheets enable the ultimate produc tion of better copy and the particular coating employed with the stencil of this invention permits the use of a thinner coating due to the hardness of the materials em ployed.

There has been described a simple, practical method of making multiple copies of any original which has outlines-thereon which will convert radiant energy to heat energy.

It will be understood that various modifications may be made in the above described stencil which provide the characteristics of this invention without departing from the spirit thereof, particularly as defined in the following claims.

We claim:

1. A heat stencilizable stencil comprising a base sheet having a weight of 4 to 5 pounds per 3,000 square feet, a thickness of from 0.8 to 1.2 mils and a minimum porosity of 200 cu. ft./ sq. ft./min,, and a coating on said base sheet uniformly applied in amounts of from 4 to pounds per 3,000 square feet, said coating consisting essentially of from 61 to 89% of a wax having a melting point from 4 160 to 210 F., and a hardness of from 5 to 10 (100 gr./ 77 F./5 sec.), from 10 to of a paraffin wax and from 1 to 4% of a wax soluble polymer.

2.- A stencilizable stencil comprising a base sheet having a weight of 4 to 7 pounds per 3,000 square feet, a thickness from 0.8 to 2.0 mils and a minimum porosity of 200 cu. ft./sq., ft./min., and a coating on said base sheet uniformly applied in amounts of from 4 to 10 pounds per 3,000 square feet, said coating consisting essentially of from 61% to 89% of a wax having a melting point from 160 to 210 F., and a hardness of from 5 to 10 gr./77 F./5 sec.), from 10 to 35% of a paraffin wax and from 1 to 4% of a wax soluble polymer.

References Cited by the Examiner UNITED STATES PATENTS 1,168,223 1/1916 Pembroke 1l735.5 2,756,161 7/1956 Horii 117--35.5 2,808,777 10/ 1957 Roshkind 117158 2,858,236 10/ 1958 Asselin et a1 1l7-68 2,877,196 3/1959 Reding 26028.5 2,927,039 3/ 1960 Vander Weel ll736.7 2,999,765 9/ 1961 Boenau 11776 3,062,675 1 1/ 1962 Shelffo 1 l735 .5

WILLIAM D. MARTIN, Primary Examiner. JOSEPH B. SPENCER, Examiner. 

1. A HEAT STENCILIZABLE STENCIL COMPRISING A BASE SHEET HAVING A WEIGHT OF 4 TO 5 POUNDS PER 3,000 SQUARE FEET, A THICKNESS OF FROM 0.8 TO 1.2 MILS AND A MINIMUM POROSITY OF 200 CU. FT/SQ. FT./MIN., AND A COATING ON SAID BASE SHEET UNIFORMLY APPLIED IN AMOUNTS OF FROM 4 TO 10 POUNDS PER 3,000 SQUARE FEET, SAID COATING CONSISTING ESSENTIALLY OF FROM 61 TO 89% OF A WAX HAVING A MELTING POINT FROM 160 TO 210*F., AND A HARDNESS OF FROM 5 TO 10 (100 GR./ 77*F./5 SEC.), FROM 10 TO 35% OF A PARAFFIN WAX AND FROM 1 TO 4% OF A WAX SOLUBLE POLYMER. 